| 摘要 |
<p>A method and apparatus for sensing the edge of a web (14) which moves along a surface (16) of a body (22) wherein an acoustic pipe is provided in the body with an opening (32) located so that the edge (12) of the web covers a portion of the opening as a function of the position of the web, an air column (20) in the pipe is caused to resonate so that the resultant acoustic signal has a frequency spectrum which is a function of the portion of the opening which is covered by the web, and the resultant acoustic signal is utilized to provide information relating to the location of the edge of the web. The opening can comprise a series of spaced apertures (32), some of which are covered by the web, or a continuous slot (100) which is partially covered by the web. The resultant acoustic signal can be analyzed by scanning a range of signal frequencies to determine the location of the edge of the web. A web width sensor comprises a pair of adjacent web edge sensors (101, 102), one for sensing the location of each web edge, for determining web width.</p> |
